1. It Will Make Room For More Interesting Storylines
No matter how much I really liked the first season of Arrow I have to admit that when it comes to plot-lines for many of the episodes it was really weak at best. Sure, the parts in which we saw Oliver trying to find the bad guys and send them to jail, as well as the development between him and his partners and the build up for the main villain were really good, however those annoying love triangles and the constant nagging from his sister were a big problem for the show's first season. In my opinion, if Arrow becomes part of a much bigger universe those problems could be reduced a lot. Since the character will be part of a much bigger universe, having to interact with characters that appear on the Superman or Batman movies and help set up new characters and elements that could be present in any of the franchises DC is planning for the Justice League film, there will be a lot of room for the writers of the show to create new and interesting plot lines to explore on the program. I know what you might think at this point "If the second season is currently being shot, how they can introduce him on time for the Justice League movie?" Here's the thing: I don't know what DC is going to do with the Justice League film, as well as what their future plans are. Considering the events of Man of Steel as well as what happened at the end of the first season, maybe there's a good way for them to show that they're in the same universe and that he will appear on future movies without having to rush an appearance for him on the movie. Here's an example: It's the end of season 2 and Oliver and the guys are just hanging out in a living room watching TV when all of the sudden the lights go out. There's no sound and everything is completely quiet. Then the TV turns on and then the camera fades to black when we hear Michael Shannon saying "You are not alone." Something like that will be all the audience will need to see that he's on the same universe and that the events of Man of Steel (as well as the sequel) will definitely have an impact on a possible season 3. I really like this show, and it would be really cool to see Stephen Amell alongside Henry Cavill and Ben Affleck on the big screen. However all I can do is sit and wait until something official is announced.